UCN Physics (OG 3204)
UCN in Fundamental Physics
The possibility to store UCN for relatively long observation times makes them unique and highly sensitive probes, testing our understanding of fundamental physics. Most of these experiments today are statistically limited and further advancements strongly depend on new high-intensity sources for UCN. A key experiment is the search for a permanent electric dipole moment of the neutron (nEDM). A finite nEDM violates time-reversal invariance and, therefore, might help to understand the matter–antimatter asymmetry in our universe. It is tightly linked to some of the open problems in modern physics, the so-called “strong CP-problem” and the “SUSY CPproblem.” Its observation would be a clear indication for physics beyond the electro-weak Standard Model of particle physics. Other important studies with UCN include determination of the neutron lifetime and decay parameters, strongly influencing our understanding of weak interactions and big bang nucleosynthesis. UCN are also being used to study fundamental quantum mechanics, search for exotic interactions, test baryon number conservation, and measure properties of the neutron itself, such as the search for a tiny but finite charge of the neutron. Learn more ...
The PSI UCN Source
A new user facility providing ultracold neutrons (UCN) for fundamental physics research, based on accelerator driven spallation neutron production and a superthermal converter, is now routinely operating (live status) at the Paul Scherrer Institut. Assembly of the PSI UCN source finished in December 2010 with the first production of ultracold neutrons. More on the UCN Source...
A new measurement of the neutron electric dipole moment (nEDM), using the Ramsey method of separated oscillatory fields, is in the data taking phase at the PSI UCN source. Already the current upper limit on nEDM (<2.9x10-26 e.cm) constrains some extensions of the Standard Model of particle physics. Our current experiment aims at a sensitivity better than 10-27 e.cm to find an eventual nEDM. More on the nEDM Collaboration